1. Field of the Invention
The present invention relates to a machine translation apparatus capable of automatically selecting a suitable translation word and reducing the burden on a user.
2. Description of the Related Art
New information is increasing rapidly in the 20th century, in what might be called a knowledge explosion age. People are impelled to perpetually enrich their knowledge in order not to be left behind the times. New knowledge comes from both inside and outside one's nation. Ordinary people read their mother language faster than foreign languages, so translations are important. It is now the time that manual translation should be replaced with mechanical translation, i.e., a machine translation system.
In a machine translation system, the language which is to be inputted for translation is called the source language, whereas the translated and outputted language is called a target language. For example, in the Japanese-Chinese machine translation system, the source language is Japanese and the target language is Chinese. The difference in syntax and semantics between the source and target languages is an important factor which influences the quality of machine translation. Consider the following translation example: ##STR1##
According to a conventional method, in order to transfer the syntax and semantics of a source language to those of a target language in a complete and precise form, the data structure of the source language is simplified to have a simple intermediate structure capable of processing a broad range of information. An example of such an intermediate structure is a dependency structure. With the simplified data structure, a translation can be processed with fewer transfer rules and with higher efficiency. This method is called the transfer system. FIG. 6 is a flow chart illustrating the translation procedure of the transfer system. As shown in FIG. 6, a machine translation apparatus using the transfer system is constructed of, in addition to a reference dictionary, (1) a source language parsing unit, (2) an intermediate structure transfer unit, and (3) a target language generating unit. The most difficult and significant operation performed by the intermediate structure transfer unit is to search for an optimum translation of a source language word. Languages have many meanings, and almost each word is polysemous. A translation word should be selected therefore in accordance with the meaning of the source word. In other words, a suitable translation word cannot be selected unless the meaning of the word in the source language can be grasped correctly. For example, the Japanese word " " has at least the following five meanings and the translation equivalents thereof change correspondingly: ##STR2##
As will be understood from the above example, it is most important for the intermediate structure transfer unit to efficiently grasp the meaning of each word of the source language. Conventional techniques dealing this subject are classified into the following two types:
(I) the user participation system, and PA1 (II) the reference dictionary system, which refers to a dictionary storing all possible translation equivalents. PA1 (1) I write a letter. PA1 (2) And, I mail the letter. PA1 1. PA1 2.
These two systems will be described below.